1. Field of the Invention
The present invention relates to an electrostatic image reproducing apparatus using a multilayered ion modulator.
2. Description of the Prior Art
It has hitherto been known a method for electrostatic image reproduction using a multilayered ion modulator in which a layer of insulating material is inserted between a pair of layers, one of which is a segmented layer of conductive material and the other of which is a continuous layer of conductive material, and said multilayered ion modulator has at least one of row of apertures formed therethrough.
FIG. 1 is a schematic view showing the principle of said prior art method for electrostatic image reproduction. As shown in FIG. 1, a corona charger 2 having a corona wire is arranged above the continuous layer of conductive material 1a of a multilayered ion modulator 1, and a member 3 for forming an electrostatic latent image of dielectric substance or photoconductor is arranged below a segmented layer of conductive material 1b of said ion modulator 1. A backing electrode 4 is arranged direct below the member 3 for forming electrostatic latent image. The member 3 for forming electrostatic latent image and the backing electrode 4 are normally made as a unit and form an electrostatic recording device. A high DC voltage is applied by a DC power source 5 on the corona wire of the corona charger 2. A high DC voltage, whose polarity is reverse to that of the above mentioned DC voltage is applied on the backing electrode 4 by the DC power source 5.
An electrostatic latent image corresponding to an image reproducing signal S can be formed on the surface of the member 3 for forming electrostatic latent image, because an ion flow which is accelerated to the backing electrode 4 is controlled according to the image reproducing signal S and passing through small apertures 1c of the ion modulator 1, when equipotential is given on the continued conductive layer 1a of the ion modulator 1 and a signal corresponding to the image reproducing signal S is applied on the segmented conductive layer 1b by a control circuit 6 while ions are being generated by the corona charger 2. In said image reproducing method for electrostatic image reproduction, a high voltage of about 2 KV is normally applied between the ion modulator 1 and the backing electrode 4.
In the transfer type electrostatic image reproducing apparatus in which an electrostatic latent image is formed on an electrostatic latent image forming member of a dielectric substance, developed by a developer and transferred on a recording paper, such devices as a developing device, a transfer device, a separating device, a charge removing device, and a cleaning device etc. are arranged in the vicinity of the member for forming electrostatic latent image. However, in the current desire for compactness of the apparatus, the space for said devices is limited, so that in view of the electrical insulation for devices or parts near the backing electrode it is undesirable to apply a high voltage on the backing electrode arranged directly below the electrostatic latent image forming member. If a high voltage is applied to the backing electrode, a strong electrical insulating treatment must be made, so that technical and economical problems arise.
The inventors have perceived the fact that the above problems in the electrostatic image reproducing process can be eliminated if whenever a high voltage is applied, the backing electrode should be grounded whereas a high voltage is applied on the ion modulator, and photon coupled isolators are used for separating electrically the ion modulator drive circuit from the image reproducing signal generating portion and the drive signal generating portion. According to the present invention, the effect of the high voltage with respect to the devices or parts near the backing electrode can be eliminated because the backing electrode is maintained at zero potential, and a high voltage need be applied only on the ion modulator and the drive circuit thereof. Furthermore, the image reproducing apparatus of the present invention is advantageous both technically and economically because the signal transmission system of the image reproducing signal and the driving signal to the driving circuit is readily treated by the usual electrical insulating technique.
Other objects and features of the present invention will be made apparent from the following description taken along with the accompanying drawings.